The purpose of this study was to assess the toxicity and efficacy of gemcitabine and docetaxel administered every other week as first-line therapy in metastatic breast cancer. Fifty-one patients with histologically confirmed metastatic breast cancer were enrolled. Patients received docetaxel 65 mg/m(2) followed by gemcitabine 2,500 mg/m(2), both on day 1 of a 14-day cycle, for 10 cycles without granulocyte-colony stimulating factor support. Thirty-five patients were evaluable for toxicity and 32 for efficacy. Median age was 65 years (range, 37 to 72 years), and median performance status was 90 (range, 60 to 100). The number of disease sites was 2 or > or =3 in 39% and 44% of patients, respectively, with visceral involvement in the liver and/or lung in 44% of patients. A total of 45% had received prior adjuvant chemotherapy. So far, 267 cycles have been administered. Twenty-five percent of the docetaxel and gemcitabine doses were reduced or delayed due primarily to neutropenia, giving a median dose intensity of 90% of the planned dose for both drugs. Grade 3/4 toxicities were mainly hematologic, with neutropenia in 46% of patients (two patients experienced neutropenic fever). Other toxicities were asthenia, diarrhea, transaminase elevation, and nausea. Overall response rate was 66% (four complete responses, 17 partial responses), with 22% of patients achieving stable disease. Responses were observed in all disease sites, including lung (60%) as well as liver (37.5%). In conclusion, preliminary evaluation from our phase II study shows that the combination of docetaxel and gemcitabine given every 2 weeks is a tolerable and highly active combination in patients with metastatic breast cancer. These data compare favorably with those obtained with other docetaxel schedules.